This invention relates to an apparatus for reducing the sound or noise generated in a chamber, such as a paint spraybooth, having airbourne liquid or solid particulates and a scrubber system located below the chamber which receives water and removes the particulates from the chamber. More specifically, the present invention relates to a noise reflector and damper for spraybooths which reflects the noise into the throat of the scrubber and reduces noise in the booth.
This application claims priority to PCT Patent Application No. PCT/US01/15016 filed on Jul. 11, 2001.
A typical spraybooth, such as the paint spraybooths used for painting of vehicle bodies by the automotive industry, comprises three basic components or sections. First, there is a painting area or section wherein the article to be painted is located or conveyed through the painting area, which generally includes paint or spray application equipment, such as robotic paint spray equipment, and one or more operators. Second, there is generally an air supply plenum located above the painting area which provides a continuous downdraft of filtered, temperature controlled air to the painting area. The air supply plenum is generally essential for maintaining paint finish quality. The downdraft pulls coating or paint overspray down, away from the article being painted and prevents the airbourne particulates from settling on the painted article and spoiling the finish. The air supply plenum also keeps the overspray away from the painting apparatus and operators. Finally, there is a scrubber system located below the painting area. In a typical paint spraybooth such as used by the automotive industry, the floor of the painting area is defined by a grate or open metal grid which is located several feet above the flood sheet and the scrubber assemblies. Typically, water or water containing various additives is flooded onto the flood sheet and received in the inlet throat of the scrubber system. The air supply and the water supply are balanced to provide either a neutral or slightly positive air pressure relative to the environment to prevent airborne dirt from being drawn into the booth. The scrubber system intermixes the air having airbourne solid or liquid particulates and the water from the flood sheet and transfers the particulates to the water, cleaning the air for recirculation or venting to the atmosphere. Upwardly opening pan-shaped shrouds have also been used on the grate above the throat of the scrubbers which may be flooded with water and catch larger articles from falling into the scrubber throat. In a typical application, the shroud has a width substantially greater than the width of the scrubber inlet and is located several feet above the inlet of the scrubber. In a typical automotive application, the grate is located about six feet above the flood sheet and the width of the shroud is more than twice the width of the scrubber inlet. Although a shroud of this type may provide some sound attenuation, particularly where the pan-shaped shroud is flooded with water, the noise reduction in the painting area resulting from the shroud is minimal.
It is well known that the noise generated by scrubber systems in the painting area of a conventional paint spraybooth of the type described above is significant and unacceptable in some applications. Even where the paint is applied to a vehicle body by robotic controlled electrostatic spray apparatus, an operator must still monitor the equipment inside the booth. There is, therefore, a longstanding need to reduce the sound generated in the painting area by the scrubber system. Various attempts have been made to reduce the noise generated in the painting area; however, the proposed solutions to this problem generally require additional costs and often do not adequately solve the problem. For example, flow through systems, wherein the water is not thoroughly intermixed with the air in the scrubber system requires a complete redesign of the scrubber system and substantial additional expense, including discreet spaced scrubber sections and a pool of water located below the scrubber tubes where the mixing takes place. Such flow through systems are also less efficient in removing the paint particulates from the air than a scrubber system wherein turbulent air and water flow is generated in the scrubber and the thoroughly mixed air and water is projected by the scrubber against an opposed separator wall. The need therefore remains to reduce the noise generated in the painting booth without reducing the efficiency of the scrubber system.
As set forth above, this invention relates to improvements in spray application systems, including paint spray application systems having an enclosed spraybooth area wherein airborne paint particles are generated and a scrubber system located below the enclosed spraybooth area to scrub the airborne particles from the spraybooth. The scrubber includes an inlet receiving water and air with airborne particles from the enclosed spraybooth area, which transfers the airbourne particles to the water, thereby cleaning the air. More specifically, this invention relates to a sound abatement device for paint spray application systems such as used by the automotive industry to paint vehicle bodies. The working floor of the spraybooth is defined by an open grate or open metal grid which is spaced several feet above a flood sheet formed by the water. The scrubber system inlet is generally level with the flood sheet. Air containing liquid or solid paint particulate is forced through the grate by the down draft created by the airflow through the plenum to the scrubber system inlet, or inlets where discreet scrubber systems are used, and through the scrubber system. Water is continuously circulated onto the flood sheet and received through the scrubber system inlet. The scrubber system is designed to transfer the airbourne particulates to the water, cleaning the air.
All scrubber systems, however, generate noise which is generated through the scrubber system into the work area above the floor. The improvement disclosed herein includes a noise reflector located directly over the scrubber system inlet which is preferably spaced from the inlet a distance equal to approximately the width of the inlet configured to reflect sound generated by or through the scrubber system back into the scrubber system inlet, thereby significantly reducing the sound generated by the scrubber system in the enclosed spraybooth work area. In one preferred embodiment, the noise reflector opens downwardly toward the scrubber system inlet reflecting the sound generated by the scrubber system into the scrubber system inlet. In another preferred embodiment, the reflector is generally arcuate opening toward the scrubber system inlet. In the most preferred embodiment, the reflector is generally semicircular, most preferably where the arc is equal to approximately two times the width of the scrubber system inlet. The noise reflector in this embodiment may be curved or faceted to focus the sound back into the scrubber system inlet.
In the testing of this embodiment of the noise reflector, it has been found that the distance between the reflector and the scrubber system inlet is important. If the noise reflector is located too close to the scrubber system inlet, it will interfere with the airflow pattern into the scrubber system inlet. However, if it is located too far from the scrubber system inlet, the efficiency of the noise reflector will be reduced or eliminated. Thus, in the most preferred embodiment, the noise reflector is located directly over the scrubber system inlet, but spaced from the inlet a distance equal to approximately the width of the inlet. This spacing provides good sound attenuation without interfering with the airflow pattern into the inlet of the scrubber system.
Similarly, testing of this invention indicated that the wider the noise reflector is, the more effective the sound attenuation. However, a noise reflector having a width substantially greater than the width of the scrubber system inlet also interferes with the airflow pattern into the scrubber system inlet. Thus, in the most preferred embodiment, the width of the noise reflector is generally equal to the width of the scrubber system inlet. Thus, a noise reflector spaced from the scrubber system inlet a distance equal to approximately the width of the scrubber system inlet and having a width approximately equal to the width of the scrubber system inlet yielded the good results while avoiding interference with the airflow pattern into the scrubber system inlet.
A further improvement in the sound attenuation provided by the noise reflector of this invention may be provided by using a sound attenuating or damping material for the noise reflector, wherein some of the noise generated by the scrubber system is absorbed by the noise reflector. In one preferred embodiment, the noise reflector is formed of a metal sheet and a laminated polymeric sheet which damps, absorbs or deadens the sound generated by the scrubber system. In the most preferred embodiment, the noise reflector is formed of a laminate having outside metallic sheets and a polymeric sheet sandwiched and laminated to the metal sheets, wherein the metallic and polymeric sheets have approximately the same thickness. The polymeric sheet may be formed of any suitable viscoelastic material, such as rubber, synthetic rubber or a polymer providing acoustical damping properties to the noise reflector by absorbing vibrational energy in the reflector. Such sound damping laminated panels have been used for damping structure-bourne sound as disclosed in U.S. Pat. No. 5,473,122 and for engine cylinder head covers as disclosed in U.S. Pat. No. 5,133,316. However, it is believed that such sound deadening laminates have not been used as a reflector as disclosed herein.
Other advantages and meritorious features of this invention will be more fully understood from the following description of the preferred embodiments, the appended claims and the drawings, a brief description of which follows.